LTE-A (Long Term Evolution-Advanced) is a further evolved and enhanced system of a 3GPP LTE system. In an LTE-A system, to meet the peak data rate requirement of the fourth generation communications technologies of the International Telecommunication Union, a carrier aggregation (CA) technology is introduced, which is also referred to as a spectrum aggregation technology or a bandwidth extension technology. In carrier aggregation, spectrums of two or more component carriers are aggregated to obtain a wider transmission bandwidth, where the spectrums of each component carrier may be adjacent continuous spectrums, or may also be nonadjacent spectrums in the same frequency band, or even discontinuous spectrums in different frequency bands. An LTE Rel-8/9 user equipment (UE) can only access one of the component carriers for data reception and transmission, whereas an LTE-A user equipment can access a plurality of component carriers at the same time to perform data reception and transmission according to capability and a service requirement of the LTE-A user equipment.
To support technologies such as dynamic scheduling and downlink multiple input multiple output (MIMO) transmission and hybrid automatic repeat request, a terminal needs to feed back to a base station uplink control information (UCI), which includes channel state information (CSI), hybrid automatic repeat request-acknowledgment information (HARQ-ACK), and a scheduling request (SR), where HARQ-ACK may also be simply called ACK (acknowledgment)/NACK (negative acknowledgment). In LTE-A, because the carrier aggregation technology is introduced, when a user equipment accesses a plurality of downlink component carriers at the same time to receive downlink data, for each downlink component carrier, the channel state information of the user equipment needs to be fed back in an uplink direction, and for data scheduled on each downlink component carrier, a hybrid automatic repeat request-acknowledgment of the user equipment also needs to be fed back in the uplink direction. Therefore, the channel state information and the hybrid automatic repeat request-acknowledgment may need to be reported on one uplink subframe at the same time, in where the channel state information to be reported may correspond to one or a plurality of downlink carriers, and the hybrid automatic repeat request-acknowledgment to be reported may also correspond to one or a plurality of downlink carriers.
The CSI includes periodic CSI and non-periodic CSI. The periodic CSI includes information such as a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indication (RI), and a precoding type indicator (PTI). The periodic CSI has multiple reporting modes on a physical uplink control channel (PUCCH). For example, in an LTE Rel-10 system, reporting modes of the periodic CSI include mode 1-0, mode 1-1, mode 2-0 and mode 2-1. One reporting mode corresponds to multiple reporting types, and different reporting types correspond to different report content. For example, in the LTE Rel-10 system, the periodic CSI includes the following several reporting types: type 1 supporting subband CQI feedback selected by a user equipment; type 1a supporting subband CQI feedback and second PMI feedback; type 2a supporting broadband PMI feedback; type 3 supporting RI feedback; type 4 supporting broadband CQI feedback; type 5 supporting RI feedback and wideband PMI feedback; and type 6 supporting RI feedback and PTI feedback.
A base station semi-statically configures a reporting mode, a reporting period and a subframe offset of the periodic CSI of each carrier through high-layer signaling. A user equipment determines, according to the reporting mode indicated by the high-layer signaling, a reporting type corresponding to a CSI to be reported, and determines, according to the reporting period and the subframe offset indicated by the high-layer signaling, a reporting moment for CSI of each reporting type. If detecting transmission on a physical downlink share channel (PDSCH) or a physical downlink control channel (PDCCH) used for indicating semi-persistent scheduling release (SPS release), a UE needs to feed back HARQ-ACK. Therefore, in a scenario of LTE-A carrier aggregation, the CSI and HARQ-ACK may need to be reported at the same time on one uplink subframe.
In an actual scenario, PDCCH loss may occur, that is, a base station sends a PDCCH to a UE, but the UE fails to detect the PDCCH, and in this case, the UE does not feed back HARQ-ACK. If in this case, periodic CSI also needs to be fed back, the UE only sends the periodic CSI to the base station, and the base station considers that the UE has fed back the periodic CSI and the HARQ-ACK at the same time, so that the base station possibly performs decoding by using an incorrect method. As a result, in one aspect, the periodic CSI cannot be correctly decoded, and in another aspect, the base station may misinterpret a part of CSI information as ACK/NACK information, causing a problem of misinterpreting discontinuous transmission (DTX) as an ACK. The DTX may indicate that the user equipment does not receive PDSCH transmission, that is, downlink data scheduled to the UE by the base station is lost. If the DTX is misinterpreted as the ACK, the base station considers that the UE receives the PDSCH and correctly receives downlink data, thereby lowering UCI transmission performance.